Regarding its abstract meaning with a person, in a way that I find similar to that of General de Gaulle’s, in a letter to Monsieur Jean-Bernard, abbé Le Blanc, Voltaire uses “en valent mieux” positively in a sentence to describe two people and the expected results when they learn more about each other’s countries :

Granted, this expression, unlike its English equivalent, strongly implies, even requires, the presence of “une influence néfaste,” and the General was well advised not to use “qu’elle ne s'en portera que mieux” in his famous speech, as it might have sounded like he was saying that the fact that all of France was “knowing, seeing, and hearing” the events in Quebec was somehow a bad thing.

I do, however, think the “Se trouver dans un excellent état" part of the expression’s meaning captures well what he meant by "en vaudra mieux” in that speech.

« Il faut parler peu, il le faut absolument. » (de Gaulle). Indeed I find the General a very clever speaker and writer, and it feels like he's very much in command of the language, so to speak. Sometimes there's like a nexus of overlapping possible phrasing that add layers to the fabric of meaning. Thanks !
– user3177Mar 6 '17 at 22:27